Window glass heating device

ABSTRACT

A window glass heating device for a vehicle is provided with a window heater configured to heat a whole area of a window glass, a window heater control unit configured to control the window heater, a camera heater that is an electric heater which heats a camera-imaging window area which is a part of the window glass included in an imaging area of a camera that images a vehicle exterior from a vehicle interior via the window glass, and a camera heater control unit configured to control supply of power to the camera heater. The camera heater control unit is configured to acquire window heater operation information, acquire a temperature of the camera heater, and control supply of power to the camera heater such that the temperature of the camera heater is within a predetermined temperature range based on the window heater operation information.

INCORPORATION BY REFERENCE

This is a continuation application of U.S. patent application Ser. No.15/686,741 filed Aug. 25, 2017, which is based on and claims priority toJapanese Patent

Application No. 2016-166493 filed Aug. 29, 2016. The disclosure of eachof the prior applications is hereby incorporated by reference in itsentirety.

BACKGROUND 1. Technical Field

The technical field relates to a window glass heating device thatprevents or removes fog of window glass of a vehicle by heating thewindow glass.

2. Description of Related Art

A window glass heating device that prevents or removes fog of(hereinafter referred to as defogging) window glass of a vehicle byheating the window glass is known (for example, see Japanese PatentApplication Publication No. 2004-189026 (JP 2004-189026 A)). The windowglass heating device supplies power to an electric heating wire which isembedded in window glass and heats the whole window glass when anoperation switch is operated by a user.

SUMMARY

Recently, vehicles including cameras for detecting objects (obstaclessuch as other vehicles and pedestrians) in front of the vehicles havebeen known. Such a camera images a vehicle exterior from a vehicleinterior via window glass (front glass).

A driver operates an operation switch to remove fog when the windowglass fogs. However, even when fog in a viewing angle area of the driveris removed, fog may remain in a camera-imaging window area which is apart of the window glass included in an imaging area of the camera. Forexample, such a problem may occur when the driver returns the operationswitch to an OFF state after a short time. In this case, an object infront of the vehicle may not be detected well.

Such a problem can be solved by providing a heater that periodicallyheats the camera-imaging window area of the window glass from the cameraside (the vehicle interior side) on the camera side to defog thecamera-imaging window area. According to this configuration, thecamera-imaging window area can always be kept in a defogged statewithout the operation switch being operated even when a user turns offthe operation switch after a short time.

However, since the heater provided on the camera side (hereinafterreferred to as a camera heater) needs to be provided in the vicinity ofthe window glass, the camera heater may be overheated by radiant heatfrom the window glass heated by the electric heating wire and heatgenerated from the camera heater. In this case, for example, there isconcern that members composed of the camera heater will be deformed andbadly affect a sensing function of the camera.

The disclosure provides a window glass heating device that canappropriately maintain a function of a camera by preventing a cameraheater from being overheated.

According to a first aspect, there is provided a window glass heatingdevice for a vehicle, including: a window heater that heats a whole areaof window glass of the vehicle to defog the window glass; a windowheater control unit that controls operation of the window heater basedon an operation on an operation switch; a camera heater that is anelectric heater which heats a camera-imaging window area which is a partof the window glass included in an imaging area of a camera that imagesa vehicle exterior from a vehicle interior via the window glass; and acamera heater control unit that controls supply of power to the cameraheater to defog the camera-imaging window area, wherein the cameraheater control unit is configured to acquire window heater operationinformation which is operation information on operation of the windowheater and to limit supply of power to the camera heater when it isestimated that the camera heater is potentially overheated by heatapplied from the window heater to the camera heater based on the windowheater operation information.

In this case, the window heater may be a deicer that includes anelectric heating wire disposed on the whole area of the window glass andthat defogs the window glass by heat generated from the electric heatingwire.

In the window glass heating device according to the aspect, the windowheater control unit may control operation of the window heater based onthe operation on the operation switch. The window heater may heat thewhole area of the window glass of the vehicle to defog the window glass.A deicer that includes an electric heating wire disposed in the wholearea of the window glass and defogs the window glass by heat generatedfrom the electric heating wire, or the like may be used as the windowheater. The “whole area of the window glass” in which the electricheating wire is disposed is an area in which one sheet of window glasscan be heated almost as a whole and does not need to include endportions of the window glass in which defogging is substantiallyunnecessary.

A camera that images a vehicle exterior (that senses an object or thelike) via the window glass may be disposed in the vehicle interior. Whenthe window glass in an imaging area of the camera fogs, imaging is notperformed well.

Therefore, the window glass heating device may include a camera heater.The camera heater is an electric heater and may heat a camera-imagingwindow area which is a part of the window glass included in the imagingarea of the camera. The camera heater control unit may control supply ofpower to the camera heater such that the camera-imaging window area isdefogged.

Since the camera heater needs to be disposed in the vicinity of thewindow glass in order to defog the camera-imaging window area, there isconcern that the camera heater will be overheated by heat received fromthe heated window glass and heat that the window glass generates.

The camera heater control unit may acquire window heater operationinformation which is operation information on operation of the windowheater and may limit supply of power to the camera heater when it isestimated that the camera heater is potentially overheated by heatapplied from the window heater to the camera heater based on the windowheater operation information. For example, the camera heater controlunit may determine whether an overheating condition in which it isestimated that the camera heater is potentially overheated is satisfiedbased on the window heater operation information and may limit supply ofpower to the camera heater when the overheating condition is satisfied.When the supply of power to the camera heater is limited, for example,the camera heater control unit may prohibit supply of power (stop supplyof power) to the camera heater or may decrease an amount of powersupplied such that an amount of heat generated from the camera heater issmaller than that in a normal state (when it is not estimated thatoverheating potentially occur).

Accordingly, the camera heater may be prevented from being overheatedand the camera heater can be maintained in a normal state. When it isestimated that the camera heater is potentially overheated, thetemperature of the camera-imaging window area is high and thus thecamera-imaging window area is defogged. Accordingly, even when thesupply of power to the camera heater is limited, the camera-imagingwindow area does not fog. As a result, it is possible to appropriatelymaintain a sensing function of the camera.

According to an aspect, the camera heater control unit may be configuredto acquire the window heater operation information including informationfor determining whether the window heater operates and to limit supplyof power to the camera heater in a period in which the window heateroperates based on the window heater operation information.

According to the aspect, the supply of power to the camera heater islimited in a period in which the window heater operates. Accordingly,the camera heater can be prevented from being overheated.

According to an aspect, the camera heater control unit may be configuredto acquire the window heater operation information including informationindicating an elapsed time after the operation of the window heaterstops and to limit supply of power to the camera heater in a period inwhich the elapsed time from stop of the operation of the window heaterdoes not reach a set time based on the window heater operationinformation.

According to the aspect, the supply of power to the camera heater islimited in a period in which the window heater operates and in a periodin which the elapsed time after operation of the window heater isstopped does not reach the set time. Accordingly, the camera heater canbe prevented from being overheated.

According to an aspect, the camera heater control unit may be configuredto control supply of power to the camera heater such that a power-supplyperiod in which power is supplied to the camera heater and anon-power-supply period in which power is not supplied to the cameraheater are alternately repeated in a period in which an ignition switchis turned on, and the camera heater control unit may be configured toacquire the window heater operation information including informationfor determining whether the window heater operates and to set thepower-supply period of the camera heater to be shorter when the windowheater operates than when the window heater does not operate.

According to an aspect, the camera heater control unit may be configuredto acquire an operating time of the window heater as the window heateroperation information and to set the power-supply period of the cameraheater to be shorter as the operating time becomes longer.

In the aspect, the camera heater control unit controls supply of powerto the camera heater such that the power-supply period in which power issupplied to the camera heater and the non-power-supply period in whichpower is not supplied to the camera heater are alternately repeated inthe period in which the ignition switch is turned on. Accordingly, thecamera-imaging window area is defogged. In this case, the power-supplyperiod and the non-power-supply period of the camera heater may beswitched, for example, based on time measured, or an estimatedtemperature of the camera heater may be calculated and both periods maybe switched based on the estimated temperature such that the estimatedtemperature is maintained within a predetermined range, or may be setarbitrarily. The ignition switch is not limited to a switch that startsan engine as a drive source of the vehicle but may be a switch thatstarts a vehicle system when it is turned on and that stops the vehiclesystem when it is turned off.

The camera heater control unit sets the power-supply period of thecamera heater to be shorter when the window heater operates than whenthe window heater does not operate. Accordingly, the camera heater canbe prevented from being overheated.

According to an aspect, the camera heater control unit may be configuredto acquire heating operation information indicating an operating stateof a heating device that heats the window glass and to set thepower-supply period of the camera heater to be shorter as a time inwhich the heating device operates becomes longer.

When the heating device operates, the temperature of the camera heaterbecomes higher when the amount of heat applied from the heating deviceto the window glass becomes larger. Therefore, the camera heater controlunit sets the power-supply period of the camera heater to be shorter asthe time in which the heating device operates becomes longer.Accordingly, the camera heater can be prevented from being overheated.For example, the camera heater control unit may calculate an estimatedtemperature of the camera heater in consideration of the time in whichthe heating device operates and stop the supply of power to the cameraheater when the estimated temperature is higher than an upper-limittemperature.

According to an aspect, the camera heater control unit may be configuredto acquire outside air temperature information indicating an outside airtemperature and to set the power-supply period of the camera heater tobe shorter as the outside air temperature becomes higher.

The temperature of the camera heater becomes higher when the outside airtemperature becomes higher. Therefore, the camera heater control unitsets the power-supply period of the camera heater to be shorter as theoutside air temperature becomes higher. Accordingly, the camera heatercan be prevented from being overheated. For example, the camera heatercontrol unit may calculate an estimated temperature of the camera heaterin consideration of the outside air temperature and stop the supply ofpower to the camera heater when the estimated temperature is higher thanan upper-limit temperature.

According to an aspect, the camera heater control unit may be configuredto acquire source voltage information indicating a source voltage whichis an output voltage of an on-board power supply device that suppliespower to the camera heater and to set the power-supply period of thecamera heater to be shorter as the source voltage becomes higher.

The camera heater generates heat to heat the camera-imaging window areaby being supplied with power from the on-board power supply device. Inthis case, a current value flowing in the camera heater and an amount ofheat generated from the camera heater become larger when the sourcevoltage which is an output voltage of the on-board power supply devicebecomes higher. Therefore, the camera heater control unit sets thepower-supply period of the camera heater to be shorter as the sourcevoltage becomes higher. Accordingly, the camera heater can be preventedfrom being overheated. For example, the camera heater control unit maycalculate an estimated temperature of the camera heater in considerationof the source voltage and stop the supply of power to the camera heaterwhen the estimated temperature is higher than an upper-limittemperature.

According to an aspect, the camera heater control unit may be configuredto acquire vehicle speed information indicating a running speed of thevehicle and to set the power-supply period of the camera heater to beshorter as the running speed becomes lower.

When the vehicle travels, the window glass is cooled by running wind.Accordingly, the temperature of the window glass becomes lower when thevehicle speed becomes higher. In other words, the temperature of thecamera heater increased by heat of the window glass becomes higher whenthe vehicle speed becomes lower. Therefore, the camera heater controlunit sets the power-supply period of the camera heater to be shorter asthe vehicle speed becomes lower. Accordingly, the camera heater can beprevented from being overheated. For example, the camera heater controlunit may calculate an estimated temperature of the camera heater inconsideration of the vehicle speed and stop the supply of power to thecamera heater when the estimated temperature is higher than anupper-limit temperature.

According to an aspect, the camera heater control unit may be configuredto prohibit supply of power to the camera heater when the window heateroperation information is not acquired.

According to an aspect, the camera heater control unit may be configuredto acquire a temperature of the camera heater and to control supply ofpower to the camera heater such that the temperature of the cameraheater is within a predetermined temperature range.

When the window heater operation information is not acquired, the cameraheater control unit cannot ascertain the operating state of the windowheater. Therefore, the camera heater control unit prohibits the supplyof power to the camera heater (stops the supply of power to the cameraheater). Accordingly, the camera heater can be prevented from beingoverheated.

According to an aspect, the camera heater control unit may be configuredto prohibit supply of power to the camera heater in a predeterminedperiod until an initial waiting time elapses after an ignition switch isturned on, to store the window heater operation information includinginformation for determining whether the window heater operates in aperiod in which the ignition switch is previously turned on in anonvolatile memory, and to set the initial waiting time after theignition switch is currently turned on to be longer when the windowheater operates in the period in which the ignition switch is previouslyturned on than when the window heater does not operate based on theinformation stored in the nonvolatile memory.

Heat generated by operation of the window heater may remain even whenthe ignition switch is turned on next time. Therefore, the camera heatercontrol unit is configured to prohibit the supply of power to the cameraheater (stop the supply of power to the camera heater) in apredetermined period until the initial waiting time elapses after theignition switch has been turned on.

Between the case in which the window heater has operated in the periodin which the ignition switch is previously turned on and the case inwhich the window heater has not operated, there is a higher likelihoodthat the temperature of the camera heater will be higher when theignition switch is currently turned on in the case in which the windowheater has operated than in the case in which the window heater has notoperated.

Therefore, the camera heater control unit stores the window heateroperation information including information for determining whether thewindow heater has operated in the period in which the ignition switchhas been previously turned on in the nonvolatile memory. Then, when thewindow heater has operated in the period in which the ignition switchhas been previously turned on, the camera heater control unit sets theinitial waiting time after the ignition switch is currently turned on tobe longer than when the window heater has not operated, based on theinformation stored in the nonvolatile memory. Accordingly, the cameraheater can be prevented from being overheated.

According to an aspect, the camera heater control unit may be configuredto prohibit supply of power to the camera heater in a predeterminedperiod until an initial waiting time elapses after an ignition switch isturned on, to store the window heater operation information includinginformation indicating a previous operating time which is a time inwhich the window heater operates in a period in which the ignitionswitch is previously turned on in a nonvolatile memory, and to set theinitial waiting time after the ignition switch is currently turned on tobe longer as the previous operating time becomes longer based on theinformation stored in the nonvolatile memory.

In the aspect, the initial waiting time is determined based on theprevious operating time which is a time in which the window heateroperates in the period in which the ignition switch is previously turnedon. In this case, the camera heater control unit stores the windowheater operation information including information indicating theprevious operating time in the nonvolatile memory and sets the initialwaiting time after the ignition switch is currently turned on to belonger as the previous operating time becomes longer, based on theinformation stored in the nonvolatile memory. Accordingly, the cameraheater can be more appropriately prevented from being overheated.

According to an aspect, the camera heater control unit may be configuredto acquire the window heater operation information including informationfor determining whether the window heater operates and may include aprohibition command issuing unit configured to output a prohibitioncommand for prohibiting operation of the window heater to the windowheater control unit when it is determined that the window heater doesnot operate based on the window heater operation information and supplyof power to the camera heater is started.

For example, when operation of the window heater is started after thesupply of power to the camera heater is started, there is concern thatthe camera heater will be overheated. Therefore, the prohibition commandissuing unit acquires the window heater operation information includinginformation for determining whether the window heater operates andoutputs the prohibition command for prohibiting operation of the windowheater to the window heater control unit when it is determined that thewindow heater does not operate based on the window heater operationinformation and the supply of power to the camera heater is started.Accordingly, the camera heater can be prevented from being overheated.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments will be described below with reference to theaccompanying drawings, in which like numerals denote like elements, andwherein:

FIG. 1 is a diagram schematically illustrating a configuration of awindow glass heating device according to an embodiment;

FIG. 2 is a front view of a vehicle;

FIG. 3 is a cross-sectional view illustrating arrangement of a cameraand a camera heater;

FIG. 4 is a timing chart illustrating a state of an ignition switch, anoperating state of a deicer, an operating state of a camera heater, andsetting of a prohibition flag;

FIG. 5 is a flowchart illustrating prohibition flag setting routine 1;

FIG. 6 is a flowchart illustrating camera heater control routine 1;

FIG. 7 is a timing chart illustrating a state of an ignition switch, anoperating state of a deicer, an operating state of a camera heater, andsetting of a prohibition flag;

FIG. 8 is a flowchart illustrating prohibition flag setting routine 2;

FIG. 9 is a timing chart illustrating a state of an ignition switch, anoperating state of a deicer, an operating state of a camera heater, anda variation of an estimated temperature of the camera heater;

FIG. 10 is a flowchart illustrating camera heater control routine 3;

FIG. 11 is a flowchart illustrating deicer operating time storingroutine 1;

FIG. 12 is a flowchart illustrating camera heater initial waiting timesetting routine 1;

FIG. 13 is a graph illustrating an initial waiting time map;

FIG. 14 is a timing chart illustrating a state of an ignition switch, anoperating state of a deicer, and an operating state of a camera heater;

FIG. 15 is a flowchart illustrating a deicer operation history storingroutine;

FIG. 16 is a flowchart illustrating camera heater initial waiting timesetting routine 2;

FIG. 17 is a flowchart illustrating a modified example of prohibitionflag setting routine 1;

FIG. 18 is a flowchart illustrating a modified example of prohibitionflag setting routine 2;

FIG. 19 is a flowchart illustrating a modified example of camera heatercontrol routine 3; and

FIG. 20 is a flowchart illustrating a deicer operation limiting routine.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, a window glass heating device according to an embodimentwill be described with reference to the accompanying drawings.

A window glass heating device according to an embodiment is a devicethat heats front window glass FG (hereinafter referred to as front glassFG) of a vehicle illustrated in FIG. 2 to defog the front glass FG. Asillustrated in FIG. 1, the window glass heating device includes anair-conditioner ECU 10 and a camera ECU 50. The ECUs 10 and 50 areelectric control units including a microcomputer as a major part and areconnected to transmit and receive information to and from each other viaa controller area network (CAN). The ECUs 10 and 50 perform apredetermined control process in a period in which an ignition switchwhich is not illustrated is turned on. In this specification, themicrocomputer includes a CPU, a ROM, a RAM, a nonvolatile memory, and aninterface I/F. The CPU is configured to embody various functions byexecuting instructions (such as programs or routines) stored in the ROM.

The air-conditioner ECU 10 includes an air conditioner control unit 20that controls air-conditioning of a vehicle interior and a deicercontrol unit 30 that controls defogging of the front glass FG. The airconditioner control unit 20 is connected to an air-conditioning device21 that air-conditions the vehicle interior. The air conditioner controlunit 20 is connected to an air-conditioning operator 22 that allows auser to perform various settings associated with air-conditioning and anair-conditioning sensor 23 which is required for air-conditioningcontrol, such as a temperature sensor. The air conditioner control unit20 controls operation of the air-conditioning device 21 based on thesetting by the air-conditioning operator 22 and a detection signal fromthe air-conditioning sensor 23. The air-conditioning device 21 alsoincludes a defogger to be described later.

The deicer control unit 30 is connected to a deicer 40 and a deicerswitch 45. The deicer 40 has a function of melting frozen ice on thesurface of the front glass FG, and is normally used to defog the frontglass FG. The deicer 40 includes an electric heating wire 41 (referredto as a deicer electric heating wire 41) embedded in the whole area ofthe front glass FG and a relay 42 (referred to as a deicer relay 42)connected in series to the deicer electric heating wire 41. The deicer40 is connected to a power supply device 100 of the vehicle.

The power supply device 100 is an on-board power supply device in whichan on-board battery and an alternator which are not illustrated areconnected in parallel, and supplies power to various on-board electricalloads including the deicer 40 and a camera heater 80 to be describedlater.

A deicer switch 45 is an operator which is operated by a user such as adriver and outputs an operation signal to the deicer control unit 30.When an ON signal is input from the deicer switch 45 in a period inwhich an ignition switch is turned on, the deicer control unit 30 turnson the deicer relay 42 to supply power to the deicer electric heatingwire 41. Accordingly, the deicer electric heating wire 41 generates heatto heat the front glass FG.

The deicer control unit 30 includes a timer and turns off the deicerrelay 42 to stop supply of power to the deicer electric heating wire 41when a predetermined time elapses from a time point at which anoperation signal is input. The deicer control unit 30 also turns off thedeicer relay 42 to stop the supply of power to the deicer electricheating wire 41 when an OFF signal is input by operation of the deicerswitch 45 before the predetermined time elapses. The deicer control unit30 does not supply power to the deicer electric heating wire 41 in aperiod in which the ignition switch is turned off.

In the following description, turning on the deicer relay 42 to supplypower to the deicer electric heating wire 41 may be referred to asoperating the deicer 40, turning off the deicer relay 42 to cut off thesupply of power to the deicer electric heating wire 41 may be referredto as stopping operation of the deicer 40, a state in which power issupplied to the deicer electric heating wire 41 may be referred to as anoperating state of the deicer 40, and a state in which power is notsupplied to the deicer electric heating wire 41 may be referred to as anon-operating state of the deicer 40 or a stopped state of the deicer40. A power-supply period in which power is supplied to the deicerelectric heating wire 41 may be referred to as an operating period ofthe deicer 40 and a non-power-supply period in which power is notsupplied to the deicer electric heating wire 41 may be referred to as anon-operating period of the deicer 40.

The camera ECU 50 includes an image processing unit 60 and a cameraheater control unit 70. The image processing unit 60 is connected to acamera 65. As illustrated in FIG. 3, the camera 65 images an externalscene in front of the vehicle from a vehicle interior via the frontglass FG and outputs image data acquired by the imaging to the imageprocessing unit 60. The image processing unit 60 detects an object (anobstacle such as a preceding vehicle, an oncoming vehicle, or apedestrian) in front of the vehicle and lane markers such as a whiteline formed on a road from image data output from the camera 65 andsupplies information indicating positions and the like thereof relativeto the vehicle to a driving support ECU (not illustrated). The drivingsupport ECU controls a running state of the vehicle based on theobstacle information, the lane marker information, or the like.

As illustrated in FIG. 3, the camera 65 is attached to a bracket 66 andis fixed to an upper position of the front glass FG with a lens facingthe front side of the vehicle. In the camera 65, a hood 67 is disposedbelow the front side of the lens such that reflected light from avehicle body does not enter the lens. The hood 67 includes a resin flatplate 67 a (referred to as a hood body 67 a) disposed in a horizontaldirection and a non-woven fabric 67 b attached to the top surface of thehood body 67 a. An electric heating wire 81 (referred to as a cameraelectric heating wire 81) is attached to the bottom surface of the hoodbody 67 a.

The hood 67 is disposed such that the surface thereof (a surface onwhich the non-woven fabric 67 b is attached) obliquely faces the frontglass FG. In the front glass FG, a part included in an imaging areawhich is used for the camera 65 to perform imaging is included in a partobliquely facing the surface of the hood 67. Hereinafter, the part ofthe front glass FG obliquely facing the surface of the hood 67 isreferred to as a camera defogging area FGC.

The camera electric heating wire 81 is connected to the power supplydevice 100 via a relay 82 (referred to as a camera heater relay 82).

A vehicle speed sensor 91, an outside air temperature sensor 92, avoltage sensor 93, and the camera heater relay 82 are connected to thecamera heater control unit 70. The vehicle speed sensor 91 outputs aspeed detection signal indicating a running speed of the vehicle to thecamera heater control unit 70. The outside air temperature sensor 92outputs an outside air temperature detection signal indicating anoutside air temperature around the vehicle to the camera heater controlunit 70. The voltage sensor 93 outputs a source voltage detection signalindicating an output voltage of the power supply device 100 to thecamera heater control unit 70.

The camera heater control unit 70 controls supply of power to the cameraelectric heating wire 81 by performing a camera heater control processto be described later to control ON and OFF of the camera heater relay82.

The hood 67 generates heat by turning on the camera heater relay 82 tosupply power to the camera electric heating wire 81, and heats thecamera defogging area FGC of the front glass FG. A device that heats thecamera defogging area FGC is a camera heater 80. Accordingly, the cameraheater 80 includes the camera electric heating wire 81, the cameraheater relay 82, and the hood 67.

A front space of the lens of the camera 65 is a sealed space surroundedby the front glass FG, the bracket 66, the hood 67, and the camera 65 (asealed space of which the front and upper sides are covered by the frontglass FG, the right and left sides are covered by the bracket 66, thelower side is covered by the hood 67, and the rear side is covered bythe camera 65).

The camera heater control unit 70 defogs the camera defogging area FGCby alternately switching a power-supply period in which the cameraheater 80 (accurately the camera electric heating wire 81) is suppliedwith power and a non-power-supply period in which the camera heater 80(or more accurately, the camera electric heating wire 81) is notsupplied with power in a period in which an ignition switch is turnedon. The camera heater control unit 70 does not supply power to thecamera heater 80 in a period in which the ignition switch is turned off.

In the following description, turning on the camera heater relay 82 tosupply power to the camera electric heating wire 81 may be referred toas operating the camera heater 80, turning off the camera heater relay82 to cut off the supply of power to the camera electric heating wire 81may be referred to as stopping operation of the camera heater, a statein which power is supplied to the camera electric heating wire 81 may bereferred to as an operating state of the camera heater 80, and a statein which power is not supplied to the camera electric heating wire 81may be referred to as a non-operating state of the camera heater 80 or astopped state of the camera heater 80. A power-supply period in whichpower is supplied to the camera electric heating wire 81 may be referredto as an operating period of the camera heater 80 and a non-power-supplyperiod in which power is not supplied to the camera electric heatingwire 81 may be referred to as a non-operating period of the cameraheater 80.

Since the camera heater 80 is disposed in the vicinity of the frontglass FG, the camera heater may be overheated by radiant heat receivedfrom the deicer 40 and heat generated from the camera electric heatingwire 81. In this case, the hood 67 may be deformed by the overheating,and good imaging of the external scene using the camera 65 may beimpossible. That is, the image processing unit 60 may not sense theexternal scene well.

Therefore, the camera heater control unit 70 prevents the camera heater80 from being overheated and maintains a satisfactory outside sensingfunction using the camera 65 (which includes the image processing unit60), by performing a camera heater control process to be describedbelow. Several examples of the camera heater control process will bedescribed below.

<Camera heater control process 1> First, a first example of the cameraheater control process (hereinafter referred to as camera heater controlprocess 1) which is performed by the camera heater control unit 70 willbe described in brief. Here, the camera heater control unit 70performing camera heater control process 1 is referred to as a firstcamera heater control unit 71. The first camera heater control unit 71defogs the camera defogging area FGC by alternately switching theoperating period (the power-supply period) in which the camera heater 80operates and the non-operating period (the non-power-supply period) inwhich the camera heater 80 does not operate. The length of the operatingperiod is set to a time tcon, and the length of the non-operating periodis set to a time tcoff.

When the ignition switch is turned on, the first camera heater controlunit 71 sets the camera heater 80 to the non-operating state andmaintains the non-operating state for the non-operating time tcoff. Whenthe non-operating state has been maintained for the non-operating timetcoff, the first camera heater control unit 71 switches the cameraheater 80 to the operating state and maintains the operating state forthe operating time tcon. In this way, the first camera heater controlunit 71 alternately switches the non-operating period set to the timetcoff and the operating period set to the time tcon. Hereinafter, thisprocess may be referred to as a basic camera heater process.

The first camera heater control unit 71 reads a deicer operating statesignal (hereinafter referred to as deicer operation information) whichis transmitted with a predetermined cycle from the air-conditioning ECU10, and monitors the operating state of the deicer 40. The first cameraheater control unit 71 prohibits operation of the camera heater 80 in aperiod matching a period in which the deicer 40 operates and a period inwhich a predetermined time tdoff elapses after the operation of thedeicer 40 ends.

FIG. 4 is a timing chart illustrating the state of the ignition switch(IG), the operating state of the deicer 40, the operating state of thecamera heater 80, and switching of a prohibition flag F. The horizontalaxis represents time. A period in which the prohibition flag F is set to“1” is a period in which operation of the camera heater 80 isprohibited. In the drawing, “ON” denotes an operating state, and “OFF”denotes a non-operating state.

As illustrated in the drawing, when the ignition switch is turned on attime t1, the first camera heater control unit 71 operates the cameraheater 80 at time t2 at which the non-operating time tcoff elapsestherefrom and sets the camera heater 80 to the non-operating state attime t3 at which the operating time tcon elapses. When operation of thedeicer 40 is started at time t4 at which the basic camera heater processis repeated, the first camera heater control unit 71 stops the operationof the camera heater 80 at that time. When operation of the deicer 40 isended at time t5, the first camera heater control unit 71 startsoperation of the camera heater 80 at time t6 at which a predeterminedtime tdoff (referred to as a stop setting time tdoff) elapses from thattime and restarts the basic camera heater process. The first cameraheater control unit 71 ends camera heater control process 1 at time t7at which the ignition switch is turned off.

In order to perform camera heater control process 1, the first cameraheater control unit 71 performs prohibition flag setting routine 1illustrated in FIG. 5 and camera heater control routine 1 illustrated inFIG. 6. The first camera heater control unit 71 performs prohibitionflag setting routine 1 and camera heater control routine 1 with apredetermined calculation cycle in the period in which the ignitionswitch is turned on.

<Prohibition flag setting routine 1> First, prohibition flag settingroutine 1 will be described. When the prohibition flag setting routineis started, the first camera heater control unit 71 reads the deiceroperation information transmitted from the air-conditioning ECU 10 inStep S11, and determines whether the deicer 40 is operating (whether thedeicer relay 42 is turned on) in Step S12. When the deicer 40 isoperating (YES in S12), the first camera heater control unit 71 sets aprohibition flag F to “1” in Step S13. The prohibition flag F indicatesthat operation of the camera heater 80 is prohibited by “1,” andindicates that operation of the camera heater 80 is permitted by “0.”

Subsequently, the first camera heater control unit 71 determines whetherthe operating state of the deicer 40 is switched in Step S14. That is,it is determined whether the operating state indicated by the deiceroperation information which is read in Step S11 before one calculationcycle and the operating state indicated by the deicer operationinformation read in Step S11 in this time are different (the operatingstate→the non-operating state, or the non-operating state→the operatingstate).

When the operating state of the deicer 40 is switched, the first cameraheater control unit 71 clears a deicer timer value td to zero in StepS15. When the operating state of the deicer 40 is not switched, thefirst camera heater control unit 71 increases the deicer timer value tdby “1” in Step S16. Accordingly, the deicer timer value td indicates anoperation duration of the deicer 40 when the deicer 40 is operating, andindicates a stop duration when the deicer 40 is stopped.

On the other hand, when it is determined in Step S12 that the deicer isnot operating, the first camera heater control unit 71 determineswhether the deicer timer value td is equal to or greater than apredetermined stop setting time tdoff in Step S17. When the deicer timervalue td is less than the stop setting time tdoff, the first cameraheater control unit 71 performs the process of Step S13. Accordingly,the prohibition flag F is set to “1.” On the other hand, when the deicertimer value td is equal to or greater than the predetermined stopsetting time tdoff, the first camera heater control unit 71 sets theprohibition flag F to “0” in Step S18 and then performs the process ofStep S14.

An initial value of the deicer timer value td (an initial value whenthis routine is started by turning on the ignition switch) is set to thestop setting time tdoff. Accordingly, at the initial time of startingthis routine, the prohibition flag F is set to “0.”

The first camera heater control unit 71 repeatedly performs suchprocesses with a predetermined calculation cycle and sets theprohibition flag F depending on the operating state of the deicer.Accordingly, as illustrated in FIG. 4, the prohibition flag F is set to“1” in the operation period of the deicer and the period until the stopsetting time tdoff elapses after operation of the deicer is stopped, andis set to “0” in other periods.

<Camera heater control routine 1> Camera heater control routine 1 willbe described below. When camera heater control routine 1 is started, thefirst camera heater control unit 71 determines whether the camera heater80 is operating (the camera heater relay 82 is in an ON state) orstopped (the camera heater relay 82 is in an OFF state) in Step S21.Since the camera heater 80 stops at the time of starting of this routine(at time t4 in FIG. 4), the first camera heater control unit 71determines whether a camera heater timer value tc is equal to or greaterthan a predetermined stop setting time tcoff in Step S22. An initialvalue of the camera heater timer value tc is set to zero.

Accordingly, at the time of starting of this routine, the determinationresult of Step S22 is “NO.” In this case, in Step S25, the first cameraheater control unit 71 determines whether the operating state of thecamera heater 80 is switched (the operating state→the non-operatingstate, or the non-operating state→the operating state). The first cameraheater control unit 71 clears the camera heater timer value tc to zeroin Step S26 when the operating state of the camera heater 80 is switched(YES in S25), and increases the camera heater timer value tc by “1” inStep S27 when the operating state of the camera heater 80 is notswitched (NO in S25). Accordingly, the camera heater timer value tcindicates an operation duration of the camera heater 80 when the cameraheater 80 is operating, and indicates a stop duration when the cameraheater 80 is stopped.

Accordingly, at the time of staring of this routine, the stop durationof the camera heater 80 is counted by the camera heater timer value tc.

The first camera heater control unit 71 repeatedly performs theseprocesses, reads the prohibition flag F, and determines whether theprohibition flag F is “0” in Step S23 when the camera heater timer valuetc reaches the stop setting time tcoff (YES in S22). The prohibitionflag F has a newest value which is set in prohibition flag settingroutine 1 which is performed in parallel with this routine.

When the prohibition flag F is “0” (YES in S23), the first camera heatercontrol unit 71 starts operation of the camera heater 80 which hasstopped in Step S24 (the camera heater relay 82 is turned on).Accordingly, power is supplied to the camera electric heating wire 81(for example, at time t2 in FIG. 4). On the other hand, when theprohibition flag F is “1” (NO in S23), the first camera heater controlunit 71 skips the process of Step S24. Accordingly, power is notsupplied to the camera electric heating wire 81.

Subsequently, the first camera heater control unit 71 performs theprocess of Step S25. In this case, when operation of the camera heater80 is started in Step S24, the operating state of the camera heater 80is switched and thus the camera heater timer value tc is cleared to zeroin Step S26. That is, counting of the operation duration is started. Onthe other hand, when operation of the camera heater 80 is prohibited,the operating state of the camera heater 80 is not switched and thus thecamera heater timer value tc is increased by “1” in Step S27. That is,counting of the stop duration is maintained.

When operation of the camera heater 80 is started, the first cameraheater control unit 71 determines whether the camera heater timer valuetc is equal to or greater than a predetermined operation setting timetcon in Step S28. When the camera heater timer value tc is less than theoperation setting time tcon (NO in S28), the first camera heater controlunit 71 reads the prohibition flag F and determines whether theprohibition flag F is “1” in Step S29. When the prohibition flag F is“0,” the routine transitions to Step S25. Accordingly, operation of thecamera heater 80 is maintained and counting of the operation duration ismaintained.

On the other hand, when the camera heater timer value tc reaches thepredetermined operation setting time tcon (YES in S28, for example, attime t3 in FIG. 4) or when the prohibition flag F is switched to “1” inthe middle thereof (YES in S29, for example, at time t4 in FIG. 4), thefirst camera heater control unit 71 performs the process of Step S30. InS30, the first camera heater control unit 71 stops operation of thecamera heater 80 (the camera heater relay 82 is turned off).Accordingly, the supply of power to the camera electric heating wire 81is cut off. Subsequently, the first camera heater control unit 71performs the process of Step S25. Accordingly, the camera heater timervalue tc is cleared to zero (S26).

The first camera heater control unit 71 repeatedly performs prohibitionflag setting routine 1 and camera heater control routine 1 with apredetermined calculation cycle. Accordingly, as illustrated in FIG. 4,operation of the camera heater 80 is limited in the period in which thedeicer 40 operates and in the period until the stop setting time tdoffelapses after operation of the deicer 40 ends. In camera heater controlroutine 1, the processes other than Steps S23 and S29 correspond to thebasic camera heater process.

In camera heater control process 1, when both the deicer 40 and thecamera heater 80 operate, the camera heater 80 is maintained in thestopped state based on an estimation result that the camera heater 80 ispotentially overheated by heat generated from the camera electricheating wire 81 and radiant heat from the deicer 40. In camera heatercontrol process 1, when the camera heater 80 operates within apredetermined time after operation of the deicer 40 is stopped,similarly, the camera heater 80 is maintained in the stopped state basedon the estimation result that the camera heater 80 is potentiallyoverheated. Accordingly, the stop setting time tdoff is set to a maximumtime in which it is estimated that the camera heater 80 is potentiallyoverheated.

According to the above-mentioned window glass heating device, operationof the camera heater 80 is limited when it is estimated that the cameraheater 80 is potentially overheated by heat applied from the deicer 40to the camera heater 80 based on the current operating state and theoperation history (whether to operate and an elapsed time after theoperation is stopped) of the deicer 4. Accordingly, the camera heater 80is prevented from being overheated. As a result, the above-mentionedproblem in the camera heater 80 does not occur and an external scene canbe imaged well using the camera 65 via the front glass FG (the externalscene can be sensed well). Since the overheated state of the cameraheater 80 can be determined without using a temperature sensor, it ispossible to put the window glass heating device into practice at a lowcost.

<Camera heater control process 2> A second example of the camera heatercontrol process (hereinafter referred to as camera heater controlprocess 2) will be described below. In camera heater control process 1,operation of the camera heater 80 is prohibited such that operation ofthe deicer 40 and operation of the camera heater 80 do not overlap eachother. On the other hand, in camera heater control process 2, when thedeicer 40 is operating, the time in which the camera heater 80 operatesis set to be short depending on the time for which the deicer 40 hasoperated. Hereinafter, the camera heater control unit 70 performingcamera heater control process 2 is referred to as a second camera heatercontrol unit 72.

For example, as illustrated in FIG. 7, when it is detected thatoperation of the deicer 40 is started at time t5 after operation of thecamera heater 80 is started at time t4, the second camera heater controlunit 72 does not stop operation of the camera heater 80 at that time butstops operation of the camera heater 80 at time t6 which is after timet5. The second camera heater control unit 72 sets the operating time ofthe camera heater 80, that is, the time from time t4 to time t6, to atime conlim which is shorter than the operation setting time tcon set inthe basic camera heater process. Here, the operation setting time tconset in the basic camera heater process is referred to as a basicoperation setting time tconbase to be distinguished from the timetconlim. Since the time tconlim is set to be variable by calculation,the time tconlim is referred to as a variable operation upper-limit timetconlim.

The second camera heater control unit 72 calculates the variableoperation upper-limit time using Equation (1).

tconlim=tconbase−C·tdon   (1)

Here, C denotes a predetermined coefficient, and tdon is a time afteroperation of the deicer 40 is started, that is, the operation durationof the deicer 40.

When the deicer 40 stops, tdon=0 is satisfied and thus the variableoperation upper-limit time tconlim is set to the same value as the basicoperation setting time tconbase. On the other hand, when the deicer 40operates, the variable operation upper-limit time tconlim is set to beshorter as the operation duration becomes longer. That is, when thedeicer 40 operates, the time in which operation of the camera heater 80is permitted is set to be shorter than when the deicer 40 does notoperate. As the operating time tdon of the deicer 40 becomes longer, thevariable operation upper-limit time tconlim is set to be shorter. Forexample, as can be seen from Equation (1), the variable operationupper-limit time tconlim varies to a negative value with an increase inthe operating time tdon of the deicer 40. Accordingly, at a time atwhich the variable operation upper-limit time tconlim becomes zero,operation of the camera heater 80 is not permitted.

Camera heater control process 2 is different from camera heater controlprocess 1, in the conditions for prohibiting operation of the cameraheater 80. Accordingly, when camera heater control process 2 isperformed, the second camera heater control unit 72 repeatedly performsprohibition flag setting routine 2 (FIG. 8) different from prohibitionflag setting routine 1 with a predetermined calculation cycle. Thesecond camera heater control unit 72 repeatedly performs camera heatercontrol routine 1 (FIG. 6) in parallel with prohibition flag settingroutine 2 with a predetermined calculation cycle. Prohibition flagsetting routine 2 includes the processes of Steps S31 and S32 inaddition to prohibition flag setting routine 1. Prohibition flag settingroutine 2 will be described below, where the processes common toprohibition flag setting routine 1 will be referenced by common stepsigns in the drawings and description thereof will not be repeated.

<Prohibition flag setting routine 2> When it is determined in Step S12that the deicer 40 is operating, the second camera heater control unit72 performs the process of Step S31. The second camera heater controlunit 72 calculates the variable operation upper-limit time tconlim usingEquation (1) in Step S31. In this case, the operation duration tdon ofthe deicer 40 in Equation (1) can be calculated from a deicer timervalue td (which is set in Steps S15 and S16). In this case, theoperation duration tdon of the deicer 40 is set to zero when the deicer40 does not operate, and is set to the same value as the deicer timervalue td when the deicer 40 operates.

Subsequently, the second camera heater control unit 72 determineswhether the operating time tcon of the camera heater 80 is equal to orgreater than the variable operation upper-limit time tconlim in StepS32. The operating time tcon of the camera heater 80 can be calculatedfrom the camera heater timer value tc. The camera heater timer value tcis calculated in Steps S26 and S27 in camera heater control routine 1.In this case, the operating time tcon of the camera heater 80 is set tozero when the camera heater 80 does not operate, and is set to the samevalue as the camera heater timer value tc when the camera heater 80operates.

When the operating time tcon of the camera heater 80 is less than thevariable operation upper-limit time tconlim (NO in S32), the secondcamera heater control unit 72 sets the prohibition flag F to “0” in StepS18. On the other hand, when the operating time tcon of the cameraheater 80 is equal to or greater than the variable operation upper-limittime tconlim (YES in S32), the second camera heater control unit 72 setsthe prohibition flag F to “1” in Step S13.

Accordingly, while the deicer 40 is operating, the variable operationupper-limit time tconlim becomes shorter with the lapse of time (as theoperating time of the deicer 40 becomes longer). Accordingly, asillustrated in FIG. 7, the time in which the camera heater 80 canoperate becomes shorter with the lapse of time from time t5 which is anoperation start time point of the deicer 40. At a time point at whichthe operating time of the camera heater 80 reaches the variableoperation upper-limit time tconlim (time t6), operation of the cameraheater 80 is stopped.

In camera heater control process 2, when the operating time tcon of thecamera heater 80 is equal to or greater than the variable operationupper-limit time tconlim which is calculated by Equation (1), the cameraheater 80 is maintained in a stopped state based on the estimationresult that the camera heater 80 is potentially overheated. In cameraheater control process 2, even in a predetermined period after operationof the camera heater 80 is stopped, the camera heater 80 is maintainedin a stopped state based on the estimation result that the camera heater80 is potentially overheated, similarly to camera heater control process1.

According to the above-mentioned window glass heating device thatperforms camera heater control process 2, operation of the camera heater80 is limited when it is estimated that the camera heater 80 ispotentially overheated by heat applied from the deicer 40 to the cameraheater 80 based on the current operating state of the deicer 40 and theoperation history of the deicer 40. Accordingly, the camera heater 80 isprevented from being overheated. As a result, the above-mentionedproblem in the camera heater 80 does not occur and an external scene canbe imaged well using the camera 65 via the front glass FG (the externalscene can be sensed well). Since the overheated state of the cameraheater 80 can be determined without using a temperature sensor, it ispossible to put the window glass heating device into practice at lowcosts.

<Camera heater control process 3> A third example of the camera heatercontrol process (hereinafter referred to as camera heater controlprocess 3) will be described below. In camera heater control process 1and camera heater control process 2, operation of the camera heater 80is prohibited based on the operating time and the stopping time of thedeicer 40. On the other hand, in camera heater control process 3, atemperature of the camera heater 80 is estimated and operation of thecamera heater 80 is controlled such that the estimated temperature ismaintained within a predetermined temperature range. Hereinafter, thecamera heater control unit 70 performing camera heater control process 3is referred to as a third camera heater control unit 73.

For example, as illustrated in FIG. 9, the third camera heater controlunit 73 controls operation of the camera heater 80 such that theestimated temperature (the temperature of the hood 67) Tx of the cameraheater 80 is within a range between a lower limit value Tmin and anupper limit value Tmax. In this embodiment, the estimated temperature Txof the camera heater 80 is calculated using the operating time of thedeicer 40, the outside air temperature around the vehicle, the vehiclespeed, the source voltage, and the heating (defogger) operating state asparameters.

In this embodiment, the estimated temperature Tx is calculated byEquation (2).

Tx=Ti+(ΔTd(t)+ΔTch(t)−ΔTa(t)+ΔTac(t))   (2)

Here, Ti denotes an initial temperature of the camera heater 80, and anoutside air temperature is used. The second term or terms subsequentthereto on the right side are terms indicating a temperature variationafter the ignition switch is turned on, where ΔTd(t) denotes a deiceroperation increase term, ΔTch(t) denotes a camera heater operationincrease term, ΔTa(t) denotes a running wind decrease term, and ΔTac(t)denotes a heating operation increase term. Here, t denotes time.

ΔTd(t) is a temperature increase by which the temperature of the cameraheater 80 increases and which is determined depending on the operatingtime of the deicer 40. The operating time of the deicer 40 is anaccumulated time in which the deicer 40 operates after the ignitionswitch is turned on (currently turned on). For example, the third cameraheater control unit 73 stores a map in which a relationship between theoperating time of the deicer 40 and ΔTd(t) which increases with anincrease in the operating time is set and calculates ΔTd(t) withreference to the map. In this case, since an amount of heat generatedfrom the deicer 40 per unit time varies depending on the source voltageoutput from the power supply device 100, it is preferable that ΔTd(t) becorrected to a higher value as the source voltage becomes higher (forexample, ΔTd(t) is multiplied by a correction coefficient depending onthe source voltage).

ΔTch(t) is a temperature increase by which the temperature of the cameraheater 80 increases and which is determined depending on the operatingtime of the camera heater 80. The operating time of the camera heater 80is an accumulated time in which the camera heater 80 operates after theignition switch is turned on (currently turned on). For example, thethird camera heater control unit 73 stores a map in which a relationshipbetween the operating time of the camera heater 80 and ΔTch(t) whichincreases with an increase in the operating time is set and calculatesΔTch(t) with reference to the map. In this case, since an amount of heatgenerated from the camera heater 80 per unit time varies depending onthe source voltage output from the power supply device 100, it ispreferable that ΔTch(t) be corrected to a higher value as the sourcevoltage becomes higher (for example, ΔTch(t) is multiplied by acorrection coefficient depending on the source voltage).

ΔTa(t) is a temperature decrease by which the temperature of the cameraheater 80 decreases by cooling of the front glass FG due to a runningwind and is calculated based on the outside air temperature and thevehicle speed. For example, the third camera heater control unit 73stores a map in which a relationship between the vehicle speed and thetemperature decreasing per unit time is set for each of a plurality ofoutside air temperatures, and calculates ΔTa(t) which is an accumulatedvalue of the temperature decrease with reference to the map. In thiscase, as the vehicle speed becomes higher, the absolute value of ΔTa(t)is set to be larger.

ΔTac(t) is a temperature increase by which the temperature of the cameraheater 80 increases by heating of the front glass FG due to heating (hotair from the defogger) and is calculated based on the heating operationtime. For example, the third camera heater control unit 73 stores a mapin which a relationship between the heating operation time and ΔTac(t)which increases as the heating operation time increases is set andcalculates ΔTac(t) with reference to the map.

<Camera heater control routine 3> FIG. 10 illustrates camera heatercontrol routine 3. The third camera heater control unit 73 repeatedlyperforms camera heater control routine 3 with a predeterminedcalculation cycle in a period in which the ignition switch is turned on.

When camera heater control routine 3 is started, the third camera heatercontrol unit 73 reads deicer operation information transmitted from theair-conditioning ECU 10 in Step S51. Subsequently, the third cameraheater control unit 73 reads parameters required for estimating thetemperature of the camera heater 80 in Step S52. In this embodiment, thethird camera heater control unit 73 reads information on the outside airtemperature which is detected by the outside air temperature sensor 92,information on the vehicle speed which is detected by a vehicle speedsensor 91, heating (defogger) operation information which is transmittedfrom the air-conditioning ECU 10, and information on the source voltagewhich is detected by the voltage sensor 93.

Subsequently, the third camera heater control unit 73 calculates theestimated temperature Tx of the camera heater 80 based on Equation (2)in Step S53.

Subsequently, in Step S54, the third camera heater control unit 73determines whether the camera heater 80 is operating (the camera heaterrelay 82 is turned on) or stopped (the camera heater relay 82 is turnedoff). Since the camera heater 80 stops at the time of starting of thisroutine, the third camera heater control unit 73 determines whether theestimated temperature Tx is lower than a first threshold value Txmin inStep S55.

When the estimated temperature Tx is lower than the lower limit valueTmin (YES in S55), the third camera heater control unit 73 startsoperation of the camera heater 80 in Step S56 (turns on the cameraheater relay 82) and then temporarily ends this routine. On the otherhand, when the estimated temperature Tx is equal to or higher than thelower limit value Tmin (NO in S55), the third camera heater control unit73 skips the process of Step S56 and temporarily ends this routine.

Although not illustrated in the flowchart, the third camera heatercontrol unit 73 skips the process of Step S56 not to start operation ofthe camera heater 80 in a predetermined time tcoff immediately after theignition switch is turned on (a period from time t1 to time t2 in FIG.9). In this case, calculation of the estimated temperature Tx of thecamera heater 80 is repeatedly performed.

When this process is repeated and operation of the camera heater 80 isstarted in Step S56, the third camera heater control unit 73 performsthe process of Step S57 after the estimated temperature Tx iscalculated. In step S57, the third camera heater control unit 73determines whether the calculated estimated temperature Tx is higherthan an upper limit Tmax. When the estimated temperature Tx is nothigher than the upper limit Tmax, this routine is temporarily ended.When this process is repeated and the estimated temperature Tx is higherthan the upper limit value Tmax due to operation of the camera heater 80(YES in S57), the third camera heater control unit 73 estimates thatthere is a likelihood that the camera heater 80 will be overheated andstops operation of the camera heater 80 in Step S58 (turns off thecamera heater relay). In this way, operation of the camera heater 80 islimited.

The third camera heater control unit 73 repeatedly performs this routinewith a predetermined calculation cycle. Accordingly, operation of thecamera heater 80 (the supply of power to the camera electric heatingwire 81) is controlled such that the estimated temperature Tx of thecamera heater 80 is within the range between the lower limit value Tminand the upper limit value Tmax as illustrated in FIG. 9. In thisexample, operation of the camera heater 80 is stopped when the estimatedtemperature Tx is higher than the upper limit value Tmax at time t3, andoperation of the camera heater 80 is restarted when the estimatedtemperature Tx is lower than the lower limit value Tmin at time t4.

When operation of the deicer 40 is started while the camera heater 80 isoperating, an increase gradient of the estimated temperature Txincreases from that time t5. This is because the deicer operationincrease term ΔTd(t) acts in Equation (2) for calculating the estimatedtemperature Tx. Accordingly, the estimated temperature Tx becomes higherthan the upper limit value Tmax earlier than when the deicer 40 does notoperate (time t6). In this way, operation of the camera heater 80 isstopped at time t6. Accordingly, the operating time of the camera heater80 is limited to be shorter.

In a period in which the deicer 40 operates even after the camera heater80 is stopped (time t6), the decrease gradient of the estimatedtemperature Tx is smaller (the temperature decreases slowly) than whenthe deicer 40 does not operate, due to an influence of radiant heatapplied from the deicer 40 to the camera heater 80. Thereafter, thedecrease gradient of the estimated temperature Tx is returned to anormal gradient from time t7 at which operation of the deicer 40 isstopped. In this way, operation of the camera heater 80 is started attime t8.

According to the above-mentioned window glass heating device thatperforms camera heater control process 3, the estimated temperature Txof the camera heater 80 is calculated based on the outside airtemperature information, the vehicle speed information, the heatingoperation information, and the source voltage information in addition tothe operation information of the deicer 40, and operation of the cameraheater 80 is controlled such that the estimated temperature Tx is withina predetermined temperature range. Accordingly, the estimatedtemperature Tx of the camera heater 80 is calculated to be higher as theoperating time of the deicer becomes longer, the outside air temperaturebecomes higher, the vehicle speed becomes lower, the operating time ofthe defogger becomes longer, and the source voltage becomes higher. As aresult, the operating time of the camera heater 80 is limited to beshorter as the operating time of the deicer becomes longer, the outsideair temperature becomes higher, the vehicle speed becomes lower, theoperating time of the defogger becomes longer, and the source voltagebecomes higher. Accordingly, the camera heater 80 is prevented frombeing overheated. As a result, the above-mentioned problem in the cameraheater 80 does not occur and an external scene can be imaged well usingthe camera 65 via the front glass FG (the external scene can be sensedwell). Since the overheated state of the camera heater 80 can bedetermined without using a temperature sensor, it is possible to put thewindow glass heating device into practice at low costs.

The third camera heater control unit 73 may calculate the estimatedtemperature Tx of the camera heater 80 based on at least one of theoutside air temperature information, the vehicle speed information, theheating operation information, and the source voltage information andthe operation information of the deicer 40, and may control operation ofthe camera heater 80 based on the estimated temperature Tx.

Modified examples which can be applied to camera heater control routines1, 2, and 3 will be described below.

<camera heater initial waiting time setting process 1> In camera heatercontrol routines 1, 2, and 3, the non-operating period in whichoperation of the camera heater 80 is prohibited is set immediately afterthe ignition switch is turned on. Camera heater initial waiting timesetting process 1 is a process of setting the stop setting time tcoffimmediately after the ignition switch is turned on to be variable.

The camera heater control unit 70 (which may be any one of the cameraheater control units 71, 72, and 73) performs deicer operating timestoring routine 1 illustrated in FIG. 11 and camera heater initialwaiting time setting routine 1 illustrated in FIG. 12 as camera heaterinitial waiting time setting process 1. First, deicer operating timestoring routine 1 will be described below. The camera heater controlunit 70 repeatedly performs deicer operating time storing routine 1illustrated in FIG. 11 with a predetermined calculation cycle in aperiod in which the ignition switch is turned on.

When deicer operating time storing routine 1 is started, the cameraheater control unit 70 reads deicer operation information which istransmitted from the air-conditioning ECU 10 in Step S61 and determineswhether the deicer 40 is operating (the deicer relay is turned on) inStep S62. When the deicer 40 is operating (YES in S62), the cameraheater control unit 70 determines whether it is immediately afteroperation of the deicer 40 is started in Step S63. That is, it isdetermined whether the deicer operation information read in a previouscalculation cycle indicates that the deicer 40 is not operating andwhether the deicer operation information read in a current calculationcycle indicates that the deicer 40 is operating.

When it is determined that it is immediately after operation of thedeicer 40 is started (YES in S63), the camera heater control unit 70clears a deicer ON timer value tdon to zero in Step S64. On the otherhand, when it is determined that it is not immediately after operationof the deicer 40 is started (NO in S63), the camera heater control unit70 increases the deicer ON timer value tdon by “1” in Step S65.Accordingly, the deicer ON timer value tdon indicates a time in whichthe deicer 40 is operating.

On the other hand, when it is determined in Step S62 that the deicer 40is not operating, the camera heater control unit 70 determines whetherit is immediately after operation of the deicer 40 is stopped in StepS66. That is, is the camera heater control unit 70 determines whetherthe deicer operation information read in a previous calculation cycleindicates that the deicer 40 is operating and whether the deiceroperation information read in a current calculation cycle indicates thatthe deicer 40 is not operating.

When it is immediately after operation of the deicer 40 is stopped (YESin S66), the camera heater control unit 70 stores the deicer ON timervalue tdon in a nonvolatile memory (EEPROM) and temporarily ends thisroutine. Accordingly, information indicating the time (the deiceroperating time) in which the deicer 40 is operating previously isstored. Thereafter, the process of Step S67 is skipped in the period inwhich operation of the deicer 40 is stopped (NO in S66).

The camera heater control unit 70 repeatedly performs deicer operatingtime storing routine 1 with a predetermined calculation cycle.Accordingly, the previous deicer operating time is stored and updated inthe nonvolatile memory whenever operation of the deicer 40 is stopped.The newest value of the deicer operating time may be stored andmaintained in the nonvolatile member even when the ignition switch isturned off.

The deicer operating time which has been stored in the nonvolatilememory in this way is used to set the non-operating period in whichoperation of the camera heater 80 is prohibited immediately after theignition switch is turned on.

The camera heater control unit 70 performs camera heater initial waitingtime setting routine 1 illustrated in FIG. 12 one time when the ignitionswitch is turned on. The camera heater control unit 70 first reads thedeicer operating time tdon stored in the nonvolatile memory in Step S71.Subsequently, the camera heater control unit 70 sets an initial waitingtime tcoff which is the stop setting time tcoff in which operation ofthe camera heater 80 is prohibited immediately after the ignition switchis turned on based on the deicer operating time tdon in Step S72.

The camera heater control unit 70 stores an initial waiting time maphaving characteristics illustrated in FIG. 13. The initial waiting timemap is a map in which the initial waiting time tcoff is set depending onthe deicer operating time tdon, and has characteristics that the initialwaiting time tcoff is set to increase as the deicer operating time tdonincreases.

The camera heater control unit 70 sets the initial waiting time tcoffwith reference to the initial waiting time map in Step S72.Subsequently, the camera heater control unit 70 clears and updates thedeicer operating time tdon stored in the nonvolatile memory to zero inStep S73, and ends camera heater initial waiting time setting routine 1.

Immediately after the ignition switch is turned on, the camera heatercontrol unit 70 prohibits operation of the camera heater 80 in a periodin which the initial waiting time tcoff elapses using the initialwaiting time tcoff set in Step S72. A predetermined constant stopsetting time tcoff is used for a second period in which the cameraheater 80 is stopped or periods subsequent thereto.

When the deicer 40 operates, heat generated therefrom may remain whenthe ignition switch is turned on next time. There is a likelihood thatthe initial temperature (the temperature when the ignition switch isturned on next time) of the camera heater 80 will be higher as theoperating time of the deicer 40 becomes longer. Therefore, in cameraheater initial waiting time setting routine 1, as illustrated in FIG.14, the initial waiting time tcoff (a time from t7 to t8) in the period(a time from t7 to t11) in which the ignition switch is currently turnedon is set as described above based on the operating time tdon (a timefrom t4 to t5) of the deicer 40 in the period (the time from t1 to t6)in which the ignition switch is previously turned on. A predeterminedconstant stop setting time tcoff is used for a second period in whichthe camera heater 80 is stopped or periods subsequent thereto (the timefrom t9 to t10).

Accordingly, by applying the initial waiting time tcoff set in cameraheater initial waiting time setting process 1 to the first stop settingtime tcoff in camera heater control routines 1, 2, and 3, it is possibleto more appropriately prevent the camera heater 80 from beingoverheated.

<Camera heater initial waiting time setting process 2> In camera heaterinitial waiting time setting process 1, the operating time of the deicer40 is measured and the initial waiting time tcoff immediately after theignition switch is turned on next time is set, but when it can bedetermined whether the deicer 40 has operated without measuring theoperating time of the deicer 40, this information can be usefully usedto set the initial waiting time tcoff to some extent. In camera heaterinitial waiting time setting process 2, an operation history indicatingwhether the deicer 40 has operated is stored in the nonvolatile memoryand the initial waiting time tcoff is set to two types of values basedon the operation history.

The camera heater control unit 70 (which may be any one of the cameraheater control units 71, 72, and 73) performs a deicer operation historystoring routine illustrated in FIG. 15 and camera heater initial waitingtime setting routine 2 illustrated in FIG. 16 as camera heater initialwaiting time setting process 2. First, the deicer operation historystoring routine will be described below. The camera heater control unit70 repeatedly performs the deicer operation history storing routineillustrated in FIG. 15 with a predetermined calculation cycle in theperiod in which the ignition switch is turned on.

When the deicer operation history storing routine is started, the cameraheater control unit 70 reads the deicer operation information which istransmitted from the air-conditioning ECU 10 in Step S81 and determineswhether operation of the deicer 40 is started in Step S82. That is, thecamera heater control unit 70 determines whether the deicer operationinformation read in a previous calculation cycle indicates that thedeicer 40 is not operating and whether the deicer operation informationread in a current calculation cycle indicates that the deicer 40 isoperating. When operation of the deicer 40 is not started (NO in S82),this routine is temporarily ended.

When this process is repeatedly performed and it is detected thatoperation of the deicer 40 is started (YES in S82), the camera heatercontrol unit 70 sets a deicer operation flag Fd to “1” in Step S83. Thedeicer operation flag Fd is information indicating whether the deicer 40has operated and an initial value thereof when the ignition switch isturned on is set to “0.”

Subsequently, the camera heater control unit 70 stores the deiceroperation flag Fd in the nonvolatile memory in Step S84 and ends thisroutine. Accordingly, when operation of the deicer 40 is detected evenonce while the ignition switch is turned on, the deicer operation flagFd indicating the operation history thereof is stored in the nonvolatilememory.

The deicer operation flag Fd stored in the nonvolatile memory in thisway is used to set the non-operating period in which operation of thecamera heater 80 is prohibited immediately after the ignition switch isturned on next time.

When the ignition switch is turned on, the camera heater control unit 70performs camera heater initial waiting time setting routine 2illustrated in FIG. 16 one time. First, the camera heater control unit70 reads the deicer operation flag Fd stored in the non-volatile memoryin Step S91. Subsequently, the camera heater control unit 70 determineswhether the deicer operation flag Fd is “1” in Step S92.

When the deicer operation flag Fd is “1,” the camera heater control unit70 sets the initial waiting time tcoff which is the stop setting timetcoff in which operation of the camera heater 80 is prohibitedimmediately after the ignition switch is turned on to a first initialwaiting time tcoff1 in Step S93. On the other hand, when the deiceroperation flag Fd is “0,” the camera heater control unit 70 sets theinitial waiting time tcoff to a second initial waiting time tcoff2 inStep S94. The first initial waiting time tcoff1 is set to be longer thanthe second initial waiting time tcoff2 (tcoff1>tcoff2).

Subsequently, the camera heater control unit 70 clears and updates thevalue of the deicer operation flag Fd stored in the nonvolatile memoryto zero in Step S95 and ends camera heater initial waiting time settingroutine 2.

Immediately after the ignition switch is turned on, the camera heatercontrol unit 70 prohibits operation of the camera heater 80 in theperiod in which the initial waiting time tcoff elapses using the initialwaiting time tcoff set in Steps S93 and S94. A predetermined constantstop setting time tcoff is used for a second period in which operationof the camera heater 80 is stopped or periods subsequent thereto.

Accordingly, by applying the initial waiting time tcoff set in cameraheater initial waiting time setting process 2 to the first stop settingtime tcoff in camera heater control routines 1, 2, and 3, it is possibleto more appropriately prevent the camera heater 80 from beingoverheated.

<Process when communication is abnormal> The air-conditioning ECU 10 andthe camera ECU 50 are connected to transmit and receive information toand from each other via a CAN, but when communication between both ECUs10 and 50 is cut off, the camera heater control unit 70 cannot receivethe deicer operation information. In this case, since the camera heatercontrol unit 70 cannot understand the operating state of the deicer 40,the camera heater 80 is maintained in a stopped state. For example, inprohibition flag setting routine 1, as illustrated in FIG. 17, theprocesses of Steps S10 and S19 have only to be added thereto. In amodified example of prohibition flag setting routine 1, the cameraheater control unit 71 determines whether communication between theair-conditioning ECU 10 and the camera ECU 50 is normal in Step S10, andsets the prohibition flag F to “1” in Step S19 when communicationbetween both ECUs 10 and 50 is cut off (when the camera heater controlunit 71 cannot receive the deicer operation information). Accordingly,when communication between both ECUs 10 and 50 is cut off, operation ofthe camera heater 80 is prohibited.

Similarly, in prohibition flag setting routine 2, as illustrated in FIG.18 (a modified example of prohibition flag setting routine 2), theprocesses of Steps S10 and S19 have only to be added thereto.

In camera heater control routine 3, as illustrated in FIG. 19, theprocesses of Steps S50 and S59 have only to be added thereto. In amodified example of camera heater control routine 3, the camera heatercontrol unit 73 determines whether communication between theair-conditioning ECU 10 and the camera ECU 50 is normal in Step S50, andmaintains the camera heater 80 in a stopped state in Step S59 whencommunication between both ECUs 10 and 50 is cut off (when the cameraheater control unit 73 cannot receive the deicer operation information).That is, the camera heater 80 is stopped when the camera heater 80operates, and the stopped state is maintained when the camera heater 80is stopped.

Accordingly, even when communication between the air-conditioning ECU 10and the camera ECU 50 is cut off, it is possible to prevent the cameraheater 80 from being overheated.

<Operation limit of deicer> For example, when operation of the cameraheater 80 is started in a state in which the deicer 40 is not operating,the camera heater 80 may be prevented from being overheated byprohibiting operation of the deicer 40, that is, causing the deicer 40not to operate even when the deicer switch 45 is operated. In this case,for example, the camera heater control unit 70 repeatedly performs adeicer operation limiting routine illustrated in FIG. 20 with apredetermined calculation cycle. The deicer operation limiting routineis performed in parallel with any one of camera heater control routines1, 2, and 3.

When the deicer operation limiting routine is started, the camera heatercontrol unit 70 reads the deicer operation information in Step S101 anddetermines whether the deicer 40 is operating in Step S102. When thedeicer 40 is not operating, the camera heater control unit 70 determineswhether a time to start operation of the camera heater 80 arrives inStep S103. When a time to start operation of the camera heater 80 doesnot arrive (NO in S103), the camera heater control unit 70 determineswhether a time to stop operation of the camera heater 80 arrives in StepS105. When a time to stop operation of the camera heater 80 does notarrive, the camera heater control unit 70 temporarily ends the deiceroperation limiting routine.

When the deicer operation limiting routine is repeatedly performed witha predetermined calculation cycle and the time to start operation of thecamera heater 80 arrives (YES in S103), the camera heater control unit70 transmits a deicer prohibition command to the deicer control unit 30of the air-conditioning ECU 10 in Step S104. Thereafter, when the timeto stop operation of the camera heater 80 arrives (YES in S150), thecamera heater control unit 70 transmits a deicer prohibition releasecommand to the deicer control unit 30 in Step S106.

When the deicer control unit 30 receives the deicer prohibition commandtransmitted from the camera ECU 50, operation of the deicer 40 isprohibited until the deicer prohibition release command is received.That is, even when a user operates the deicer switch 45, the deicercontrol unit does not accept the switch operation.

Accordingly, operation of the deicer 40 is not started. Accordingly,operation of the deicer 40 is not started while the camera heater 80 isoperating and it is thus possible to prevent the camera heater 80 frombeing overheated.

While the window glass heating device according to an embodiment hasbeen described above, the disclosure is not limited to the embodimentand can be modified in various forms without departing from the conceptof the disclosure.

For example, in camera heater control process 2, the variable operationupper-limit time tconlim is changed by only the operation duration tdonof the deicer 40, but may be changed depending on at least one of theoutside air temperature, the source voltage, the vehicle speed, and theheating (defogger) operating state in addition to the operation durationtdon of the deicer 40. In this case, the variable operation upper-limittime tconlim can be set to be variable such that it becomes shorter asthe outside air temperature becomes higher, it becomes shorter as thesource voltage becomes higher, and it becomes shorter as the vehiclespeed becomes lower.

In this embodiment, when operation of the camera heater 80 is limited,the camera heater relay 82 is turned off to set the amount of powersupplied to zero, but this need not to be performed and generation ofheat of the camera heater 80 may be limited, for example, by supplyingthe camera electric heating wire 81 with an amount of power smaller thanthat in a normal state (when it is not estimated that there is alikelihood that the camera heater 80 will be overheated). In adjustingthe amount of power supplied, a current value flowing in the cameraelectric heating wire 81 may be adjusted or a power-supply time ratio(power-supply time/(power-supply time+non-power-supply time)) of thecamera heater may be adjusted.

This embodiment provides a window glass heating device which is disposedon front window glass FG, but may be applied to a window glass heatingdevice which is disposed on rear window glass. In this case, the camera65 images an external scene in the rear of the vehicle from the vehicleinterior via the rear window glass.

What is claimed is:
 1. A window glass heating device for a vehicle,comprising: a window heater configured to heat a whole area of a windowglass of the vehicle to defog the window glass; a window heater controlunit configured to control the window heater; a camera heater that is anelectric heater which heats a camera-imaging window area which is a partof the window glass included in an imaging area of a camera that imagesa vehicle exterior from a vehicle interior via the window glass; and acamera heater control unit configured to control supply of power to thecamera heater to defog the camera-imaging window area, wherein thecamera heater control unit is configured to: acquire window heateroperation information which is information on operation of the windowheater, acquire a temperature of the camera heater, and control supplyof power to the camera heater such that the temperature of the cameraheater is within a predetermined temperature range based on the windowheater operation information.
 2. The window glass heating deviceaccording to claim 1, wherein the window heater is a deicer thatincludes an electric heating wire disposed on the whole area of thewindow glass and that defogs the window glass by heat generated from theelectric heating wire.
 3. The window glass heating device according toclaim 1, wherein the camera heater control unit is configured to acquirethe window heater operation information including information fordetermining whether the window heater operates, and limit supply ofpower to the camera heater in a period in which the window heateroperates based on the window heater operation information.
 4. The windowglass heating device according to claim 1, wherein the camera heatercontrol unit is configured to control supply of power to the cameraheater such that a power-supply period in which power is supplied to thecamera heater and a non-power-supply period in which power is notsupplied to the camera heater are alternately repeated in a period inwhich an ignition switch is turned on, and the camera heater controlunit is configured to acquire the window heater operation informationincluding information for determining whether the window heateroperates, and set the power-supply period of the camera heater to beshorter when the window heater operates than when the window heater doesnot operate.
 5. The window glass heating device according to claim 4,wherein the camera heater control unit is configured to acquire outsideair temperature information indicating an outside air temperature, andset the power-supply period of the camera heater to be shorter as theoutside air temperature becomes higher.
 6. The window glass heatingdevice according to claim 4, wherein the camera heater control unit isconfigured to acquire source voltage information indicating a sourcevoltage which is an output voltage of an on-board power supply devicethat supplies power to the camera heater, and set the power-supplyperiod of the camera heater to be shorter as the source voltage becomeshigher.
 7. The window glass heating device according to claim 4, whereinthe camera heater control unit is configured to acquire vehicle speedinformation indicating a running speed of the vehicle, and set thepower-supply period of the camera heater to be shorter as the runningspeed becomes lower.